1. Macro Cellular Wireless Networks
Many people use mobile stations (e.g. cell phones and personal digital assistants (PDAs)) to communicate with macro cellular wireless networks (i.e. wireless wide area networks (WWANs)), which typically provide communication services such as voice, text messaging, and packet-data communication. These mobile stations (i.e. access terminals) and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless protocol (e.g. CDMA (Code Division Multiple Access), EV-DO (Evolution Data Optimized), and/or one or more others). Mobile stations typically conduct wireless communications with these networks via one or more base transceiver stations (BTSs), each of which send communications to and receive communications from mobile stations over the air interface.
Each BTS is in turn connected with a network entity known as a base station controller (BSC) (i.e. radio network controller (RNC)), which controls one or more BTSs and acts as a conduit between the one or more BTSs and one or more switches or gateways, such as a mobile switching center (MSC) and/or a packet data serving node (PDSN). The one or more switches or gateways may then interface with one or more signaling and/or transport networks. As examples, an MSC may interface with the public switched telephone network (PSTN), while a PDSN may interface with one or more core packet data networks and/or the Internet. As such, mobile stations can typically communicate over the one or more signaling and/or transport networks from anywhere inside the coverage area of one or more BTSs, via the BTS(s), a BSC, and a switch or gateway such as an MSC and/or PDSN.
The base stations (i.e. BTSs or combinations of (1) one or more BTSs and (2) a BSC) for these macro cellular networks are typically not associated with any subscriber or small group of subscribers in particular; rather, they are placed in publicly-accessible locations and are used by the service provider's customers generally. These base stations collectively blanket cities, rural areas, etc. with coverage; as such, they are referred to generally and herein as macro (or macro-network) base stations, and the network they collectively form—or to which they collectively belong—is referred to generally and herein as the macro network. And the BTSs associated with macro networks may be referred to herein as macro BTSs (or just BTSs).
Mobile stations and macro base stations conduct communication sessions (e.g. voice calls and data sessions) over frequencies known as carriers (i.e. macro carriers), each of which may actually be a pair of frequencies, with the base station transmitting to the mobile station on one of the frequencies, and the mobile station transmitting to the base station on the other. This approach is known as frequency division duplex (FDD). And the base-station-to-mobile-station link is known as the forward link, while the mobile-station-to-base-station link is known as the reverse link. Note that an instance of a carrier in a macro coverage area referred to as a sector may be known and referred to herein as a sector-carrier or macro sector-carrier.
2. Femtocells
Many macro-network subscribers, including private consumers and small businesses, among others, in addition to having wireless service (which may include data service) for their respective mobile stations, also have high-speed (a.k.a. broadband) Internet access through another communication channel, which may be cable-modem service, digital-subscriber-line (DSL) service, satellite-based Internet service, and/or some other option or combination thereof.
In a typical arrangement, a user may have a cable modem connected (a) via coaxial cable to a cable provider's network and (b) via Ethernet cable to a wireless (e.g. IEEE 802.11 (WiFi)) router. That router may include one or more Ethernet ports to which computers or other devices may be connected, and may also include wireless-access-point functionality, providing a wireless packet-data interface to, e.g., laptop computers, digital video recorders (DVRs), appliances, and/or any other computing devices or their respective wireless network adapters.
To address gaps in macro-network coverage (e.g. in buildings) and for other reasons, macro-network service providers offer consumers devices referred to herein as femtocells, which may also be referred to as femto base stations, femto BTSs, picocells, pico base stations, pico BTSs, microcells, micro base stations, micro BTSs, and by other names, such as Internet base stations or perhaps low-cost Internet base stations (LCIBs). Note that the aforementioned terms that end in “cell” may also be used generally and herein to refer to the coverage area provided by the respective device. And with respect to the term LCIB, low-cost is not used as a limiting term; that is, devices of any monetary cost may be categorized as LCIBs, though most LCIBs typically will be less expensive on average than most macro-network base stations.
A femtocell may be approximately the size of a desktop phone or WiFi access point, and is essentially a low-power, low-capacity version of a macro base station. Thus, a femtocell may use a power outlet, perhaps with a transformer providing a DC power supply. The femtocell may have a wired (e.g. Ethernet) or wireless (e.g. WiFi) connection with the user's router, and would thus have connectivity to the Internet and/or one or more other packet-data networks via that broadband connection. A femtocell may establish a virtual-private-network (VPN) connection over the Internet with an entity (e.g. a VPN terminator) on the wireless-service (macro-network) provider's core network, and thereby be able to securely communicate via the VPN terminator with other entities on that core network and beyond.
A typical femtocell also has a wireless-communication interface (operating according to, CDMA, EV-DO, and/or one or more other protocols) that is compatible with the user's mobile station(s), such that the femtocell may act as a micro base station, providing coverage for the mobile station(s) on the macro-network provider's network via the user's Internet connection. Usually, a femtocell provides service on a single RF carrier (or on a single carrier per protocol, if multiple protocols (e.g. CDMA and EV-DO) are supported), and transmits what is known as and referred to herein as a pilot beacon, which is a radio beacon that includes overhead messages and parameters that mobile stations use to connect with (i.e. handoff to) the femtocell.
A femtocell typically emits the pilot beacon on one or more macro carriers on which service is provided by the surrounding macro network. If service is provided by the surrounding macro network on only one macro carrier, the femtocell will emit its pilot beacon on that macro carrier. If, as is often the case, service is provided by the surrounding macro network on multiple macro carriers, the femtocell may sequentially step through emitting its pilot beacon on some number of those carriers; that is, the femtocell's pilot beacon may “hop” on a fixed number of macro carriers, and in that scenario is referred to as a frequency-hopping pilot beacon.
And femtocells typically include a Global Positioning System (GPS) receiver for use in receiving and decoding GPS signals, for use in determination of location, as well as for use in synchronizing operations with other femtocells and/or the macro network, based on timing information embedded in GPS signals. Typically, femtocells have fairly comprehensive auto-configuration capabilities, such that they are largely “plug-and-play” to the user.